The present invention relates to a metal cord for reinforcing rubber articles and a pneumatic tire including metal cords to reinforce tire components such as the carcass, the breaker and the band.
In recent years, from the viewpoint of protection of the environment, there is a pressing need to reduce the weight of automobile tires because the tire weight reduction may decrease the rolling resistance and improve the fuel consumption of the automobiles. Therefore, every effort to reduce the tire weight has been made on various tire components.
For example, in case of steel cords used to reinforce pneumatic tires, effort to increase the strength of a cord is made in order to decrease the total weight of steel cords used in a tire. Therefore, we tried to increase the strength of steel filaments constituting a steel cord, using various materials for example a wirebar made of a high-carbon steel whose carbon content is in a range of from 0.90 to 1.0 weight % or a low-alloy steel including chromium, and changing the wire drawing conditions so as to be able to uniformize heat the generation during drawing and the amount of processing to the drawn wire or filament, and further changing the thermal treatment process. As a result, there is hope for desired high-strength filaments.
In such high-strength steel filaments, however, the resistance to fatigue is not good. It is difficult to improve the fatigue resistance at the same time by the process which is capable of improving the tensile strength.